Under the management of Mr. John Fox the clay-works of the Coalbrookdale
Company have become so expanded and improved, that they now form an
important department of the Company’s undertakings, and are at the
present juncture, no doubt, among the more profitable of their
industries. Since sanitary science has so successfully called public
attention to the importance of the use of good bricks impervious to damp,
the productions from these excellent coal-measure clays have been more in
demand. Clays, as commonly understood, mean earth of sufficient
ductility to allow of being kneaded into some useful shape or form, and
rank as raw materials. Some are soft, others are indurated, or hard and
rocky; but all have in one sense been prepared by certain poundings,
grindings, washings, and mixings, carried on by Nature on a larger scale
than that on which they are now still further fitted for use. They
differ in quality, in degree of fineness, and in colour, and show certain
relationships by which it is clear that they are descended from sand,
just as sands are descended from a hardy race of pebbles, which in turn
bear close relationship to rocks, from which undoubtedly they have been
derived. Surface clays used for making inferior bricks and tiles, whose
earthy odour gives evidence of alumina, are generally derived from red
sandstone rocks, ground down into mud by the machinery of waves or
streams whilst our deeper coal-measures clunches, and clays were
originally the sediment thrown by rivers at their embouchures into inland
lakes or seas, and are usually much more free from lime, iron, grit, and
other foreign substances and impurities.
When brought to the surface, these clays are hard as a rock. Formerly
they were allowed to lie during the winter to weather, as it is called;
and a statute now obsolete required, under a heavy penalty, that bricks
should not be made unless the clay for making them had been turned over
at intervals, three times at least before the first of March. But
brickmakers, not having patience to wait for the action of the weather,
have invented machinery to do the work, and the clay is taken direct from
the pit to be crushed by iron rollers, and then conveyed by coarse
canvas-screens to tanks to be moistened, and afterwards to the pug mill.
This is an upright cylinder, with a revolving vertical shaft, fitted up
with horizontal knives following each other at an angle so as to cut,
amalgamate, and temper the material, and which also acts as a screw to
deliver it.
Ornamental bricks of elaborate design for architectural purposes require
more delicate manipulation, and the clays for these undergo a more
careful preparation. Machines in some instances are used, which take the
clay, temper, thoroughly amalgamate it, and convert it into the finished
article, and at the brick-yards of the Coalbrookdale Company presses have
been erected by which bricks may be stamped at once from the semi-dry
clay.
This company, too, have been at great pains to turn their clays to
account by copying the Italian and Lombard style of making bricks of
various forms and colours; and the buildings erected with these bricks,
and others, with white facings of the same material, of which the present
Literary and Scientific Institute is an example, possess great
architectural beauty. Still further examples of the æsthetic treatment
of these admirable clays were made a short time ago by Monsieur Kremer,
who modelled and prepared at the company’s Lightmoor clay works, in
relief, and on a large scale, an historical subject, connected with
Scottish history in the time of King James, as a facade for a house in
London; also some noble groups, life size, of figures representing the
four seasons, for a gentleman’s grounds and park near London. The reader
may judge of the adaptability of these clays for such purposes by
inspecting a group of a similar kind in front of the Institute.
We exhibited ourselves in 1851 specimens of these and other coal-measure
clays, with articles manufactured from them on both sides the river, and
we had the satisfaction of hearing from distinguished judges, familiar
with their merits, such as presidents of foreign Academics of Science,
speak of them as superior to any they had ever seen. {306}
[Picture: Swamp]